1. Field of the Invention
The present invention related to a bearing structure in which a resin bush is inserted into a bearing hole formed in one constituent member, and a support shaft protruding from the other constituent member is inserted into the bearing hole through the resin bush so as to be rotatbly supported thereon.
2. Description of the Related Art
JP-2005-287724-A discloses an armrest provided on a side of a vehicle seat. In JP-2005-287724-A, a support shaft extends from a backside frame of the vehicle seat, bearing holes are formed in facing frames of the armrest at a base portion, and the support shaft is inserted into the bearing holes to support the armrest in the width direction. The armrest is stored at a side of a seat back in an erected state and forwardly reclined from the erected state with the support shaft as a pivot.
In the armrest, an arc-like guide hole is formed in a plate face of the armrest frame with the support shaft as a center, a stopper pin for regulating a rotation range of the armrest is protruded from a plate face of the backside frame at a position apart from the support shaft and inserted into the guide hole, and a hook-like lock cam is provided to the backside frame to be engageable with the stopper pin to thereby store the armrest at the side of the seat back in the erected state.
In the armrest, metal bushes are mounted onto the stopper pin to smoothen engagement/disengagement of the lock cam with/from the stopper pin.
In the metal bushes, a cylindrical portion (main body) is fitted with the stopper pin, a flange is formed at one end of the cylindrical portion, an inner cylindrical surface of the cylindrical portion and a flange surface of the flange faced to the armrest frame are coated with a resin having a low frictional coefficient (see JP-2005-287724-A).
Here, when further bushes for the support shaft are provided in addition to the bushes for the stopper pin, a rotational movement of the armrest can be further smoothened.
However, when the metal bushes are mounted into bearing holes of the armrest frames for inserting the support shaft therethrough, since an excessive load is applied to the support shaft during the use of the armrest, the resin coating of the bushes may be easily abraded. Further, since the bushes are formed of metal, it is necessary to process the cylinder end of the cylindrical portion or the shaft end of the support shaft so as to prevent the bushes from dropping from the bearing holes, and workability for the assembly is deteriorated.
By using a resin bush instead of the metal bush, the above-mentioned drop-out prevention process may be omitted with a simple structure. However, when the resin bushes are mounted into the bearing holes for inserting the support shaft to support the armrest, since an excessive load is applied to the support shaft during the use of the armrest as described above, the bushes may be crushed and destroyed.